Coinfection With Multiple Nontuberculous Mycobacteria as a Possible Exacerbating Factor in Pulmonary Nontuberculous Mycobacteriosis: Clone Library Analysis Using the 16S Ribosomal RNA Gene

Abstract

Mycobacterial culture is the gold standard for the diagnosis of nontuberculous Mycobacterium (NTM) infections. However, this method is not suitable for detection of coinfection with different NTMs. The goal of this study was to determine if clone library analysis of BAL fluid (BALF) was useful for detection of NTM phylotypes, including multiple NTM phylotypes, in pulmonary NTM infections. BALF samples obtained from 120 patients with suspected pulmonary NTM infections were retrospectively evaluated by using the mycobacterial culture and clone library methods between July 2010 and August2016. In total, 55 (45.8%) patients were diagnosed as NTM positive according to results of mycobacterial culture, and 52 patients were NTM positive as determined by using the clone library method. Furthermore, 45 (86.5%) and seven (13.5%) patients exhibited a single phylotype (mono-phylotype group) and multiple phylotypes of NTM (multi-phylotype group), respectively. Compared with the mono-phylotype group, the multi-phylotype group had a significantly higher incidence of adverse chest CT findings (P= .048). In addition, 11 patients who were NTM negative according to results of BALF mycobacterial culture were determined to be NTM positive according to the clone library method. Six of these 11 patients were eventually diagnosed as NTM positive by using mycobacterial culture results within 6.2 ± 2.1months following the initial sample collection. Coinfection multiple phylotypes could be associated with adverse clinical findings. In addition, patients who test positive for NTM genes but negative for mycobacterial culture may be diagnosed with NTM lung infection within 1 year of the initial sample collection. Further follow-up of these patients may facilitate early detection of NTM species.